On January 20, 2014, Mercier was signed to a three-year contract extension by Genève-Servette.[1] Mercier won the 2014 and 2015Spengler Cup with Geneva.
On May 17, 2016, Mercier agreed to a two-year contract extension with Geneva.[2] During the 2016–17 season, Mercier played his 542nd regular season game with Geneva in the NL, becoming the all-time leader in term of games played for Genève-Servette.
On December 28, 2018, Mercier signed an early two-year contract extension with the team through the 2020/21 season.[3] On January 16, 2021, Mercier was suspended for 7 games and fined CHF 5,700 after he accidentally bumped into a referee in a game against HC Ambrì-Piotta on January 12, 2021.[4] Servette appealed the decision and both the suspension and the fine were eventually reduced to 3 games and CHF 2,520 on January 21, 2021.[5]
On April 6, 2021, Merci was signed to an early one-year contract extension by Servette through the 2021/22 season.[6]
Mercier retired from professional hockey following the 2021–22 season.
His father Alain Mercier also played professional hockey with Genève-Servette HC from 1985 to 1991. He appeared in 98 Swiss League games and was also a defenseman.
